Many materials such as cement, pebble lime, and powders are carried as hulk cargo in ships and barges. Cargo of this type is generally off-loaded by large-size vacuum systems. The vacuum airflow generated by these systems is typically compressor-driven by a number of diesel-powered engines. As the material is off-loaded, it is pulled into a cyclone device where the airflow is separated from the entrained material. There, the material is moved onward by gravity flow or alternative means.
The airflow is separated from entrained material via large filters which are positioned across openings in a tube sheet or barrier wall within the cyclone device. Typically, the barrier wall is a horizontal or vertical plate. Oftentimes, two dozen or more circular filter openings, usually one foot in diameter or less, are distributed around and across the harrier wall.
Prior to the present invention, filters were individually mounted across barrier wall openings. They were installed by means of an annular mounting plate bolted into position on one side of the barrier wall. An end of a filter basket extended through the wall opening and was bolted directly to the mounting plate. The filter basket held a single filter against the mounting plate.
The space on the filter-side of the barrier wall is a dirty area where both the airstream and entrained material are received. The air is separated by pulling it through the filters by one or more large compressors. By necessity, the filtered air must subsequently pass directly through the compressors.
It is critical that the filters be sealed effectively. Otherwise, debris can be sucked through the barrier wall and into the compressors, thereby causing extensive damage that can literally destroy them. This is a significant problem because the cost of replacing a compressor can range from $40,000 to in excess of $100,000, depending on system size and design.
In this respect, one of the problems associated with the above design is that basket-held filters are not tightly clamped against the mounting plate by the filter basket. This impairs the effectiveness of the filter-to-plate seal. In recognition of this drawback, attempts have been made to pull the filter tightly against the mounting plate by means of threaded bolts having ends engaged directly with the filter, while, at the same time, the filter is held in place by the basket. This technique has met with questionable success.
Moreover, the above design, in combination with the large size of the filters (typically one foot in diameter by five feet in length), presents significant maintenance problems. Each filter eventually becomes fouled and must be replaced. This involves the erection of scaffolding on the dirty side of the barrier wall in order to support workmen while they remove and reinstall filter baskets. Workmen are also required on the opposite or clean side of the barrier wall to assist in bolting the basket into place. This process has been very expensive in terms of labor costs, because of the many days and large crew of workers required.
The present invention makes filter replacement quick and easy by a single workman operating solely from the clean side of the barrier wall. A single workman using the invention can replace a battery of filters in literally a few hours as opposed to the many days required by the prior design.